Several different types of transducers are known for utilization in graphic communications systems to provide coordinate-position-indicating electrical signals. One type of known transducer, described in U.S. Pat. No. 3,699,439, includes first and second sets of terminals in contact with the edges of a sheet of material having substantially uniform resistivity. Preassigned input electrical signals are alternately applied to the two sets of terminals, and a writing stylus is utilized by an operator to establish direct contact or capacitive coupling to the resistive sheet. In that way successive x- and y-direction output signals indicative of the position of the stylus are provided.
Another type of known transducer is designed to be employed in combination with a light-emitting stylus adapted to be manipulated by an operator to define graphical information on the surface of the transducer. One such transducer is described, for example, in U.S. Pat. No. 3,944,740.
Moreover, the transducer device described in U.S. Pat. No. 3,944,740 is further adapted to be combined with an associated display panel. In that way the graphical information being written into the device by an operator can be viewed during and subsequent to the writing process.
Considerable interest exists on the part of workers in the communications field in providing a light-actuated transducer of the general type described above. An inexpensive and reliable device of this type can provide an attractive way of generating coordinate-position-indicating signals to be inputted to a computer or to be transmitted to a remote location where the graphical input information is to be reproduced. At the same time it is often desired that the graphical information being written into the transducer be viewable locally by the person doing the writing.